karthik rheology

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    RESEARCH ON RHEOLOGY

    R.Karthik

    PA/2010/09 1

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    Topics covered

    SelectionofPectin as pharmaceuticalexcipient on the basis of

    Rheological behavior

    Determinationofoptimal combinationofsurfactants in

    creams using rheology measurements

    Rheological investigationofSelfEmulsificationprocess

    Rheological analysis ofstabilityofpharmaceutical suspensions

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    The aim ofthis study was to evaluate rheological properties of pectin solutions

    to determine the influence of polymer concentration, pH, preservatives and

    heating duration on viscosity, using Brookfield R/S Plus Rheometer. The

    results shows that dilute pectin solutions are showing Newtonian, but at a

    moderate concentration they exhibit the non-Newtonian behavior, and the

    psudoplastic nature was found to increase with concentration. As the pH of

    the polymer solution lowered there was increase in viscosity of the system

    observed, this may be due do the carboxyl acid groups on the pectin chains

    are neutralize i.e. reduction in ionization, and leads to reduction in hydration

    of the carboxylic acid groups. As a result of reduced ionisation, thepolysaccharide molecules do not repel each other over their entire length. The

    result shows that pectin solutions are stable at broad range of pH. It was

    observed that as the temperature or pH of the system increases there was

    decrease in viscosity.

    SelectionofPectinaspharmaceuticalexcipient on

    the basisofRheological behavior

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    Purpose. Aimofthestudyistoexploretheviscoelastic propertiesofintermediate

    liquidcrystalline (LC) phaseformedduring self-emulsification and toevaluate its

    influenceon self-emulsification

    performance.

    Methods. Binarysystemoftween 80 (T80)andimwitor 742 (I742)was used and

    different SES werepreparedwith I742 at 10, 30,50,70 and 90% w/w concentration

    levels. Self-emulsificationwas monitored byvisualobservations anddroplet size

    measurement. Mesophases obtained by50% v/v aqueous hydrationofSESwere

    utilizedfor polarizing microscopy,differential scanning calorimetry and rheologicalstudies.

    RheologicalinvestigationofSelfEmulsificationprocess

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    Results

    SES 30% presented good emulsifying properties and nano-size dropletswere observed after its emulsification as compared to micron sized droplets for

    other SES. In polarizing microscopy, formation of intermediate LC phase was

    observed in all SES. Lamellar phase was evident in 30% SES while other SES

    exhibited micellar cubic phase. Presence ofhigh level ofstructurally bound water

    in thermal analysis confirmed mesophase formation in all SES. Thus, rheological

    studies concluded presence of weak and fragile mesophase structure in 30% SES

    while LC phase structure with little structural build up was observed in other SES.

    This weak mesophase structure in SES 30% presented no or very little resistance

    against strain induced deformation. Therefore, during emulsification, weak

    mesophase in SES 30% ruptured with ease and released jet of nano-size droplets

    compared to coarse droplets for other SES.

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    compliance= strain/stress

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    Rheologicalanalysisofstabilityofpharmaceutical

    suspensions

    Viscometry: The samples were exposed to increasing stress (0.1-100 Pa) and relation

    between shear stress and shear rate was studied.

    Oscillation stress sweep: Linearviscoelastic region (LVR) was determined

    in the stress range of0.1-100 Pa at aconstant frequency (1 Hz). The ability of

    hydrated SES to resist the deformation with applied stress was recorded in terms of

    trends of elastic modulus (G) and loss modulus (G).

    Oscillation frequency sweep: The samples were exposed to increasing frequency (0.1-

    10 Hz) at a constant stress in LVR. Effect of frequency on G, G, phase degree () and

    loss tangent (tan ) were recorded.

    Creep-recovery: SES samples were exposed to a constant stress in LVR for

    100s. It was then instantly removed and the recovery was followed for 200s. The creep

    compliance, J (defined as ratio between measured strain and applied stress) was

    recorded against time.

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    Shear stress

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    References

    Rheological EvaluationofSilicon/Carbopol Hydrophilic GelSystems as a Vehicle

    for DeliveryofWater Insoluble Drugs Giulia Bonacucina,1 Marco Cespi,1 Monica Misici-Falzi,

    and Giovanni F. Palmieri1,2

    Rheological InvestigationofSelf-emulsification Process

    Shailesh V. Biradar, Ravindra S. Dhumal, Anant Paradkar

    Department ofPharmaceutics,Bharati Vidyapeeth University, Poona CollegeofPharmacy,

    Erandwane, Pune 411 038, Maharashtra State, India

    SELECTION OF PECTIN AS PHARMACEUTICAL EXCEPIENT ONTHE BASIS OF RHEOLOGICAL

    BEHAVIOR RAJENDRA AWASTHI Laureate InstituteofPharmacy, Kathog 177101, (Teh. Dehra, Dist. Kangra,

    HP), India

    Rheological Analysis oftheStabilityofPharmaceuticalSuspensions

    Eva-Maria Kutschmann, Gebrder Haake, Dieselstrasse4, D - 76227 Karlsruhe

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